Tubular column for gas injection well

Abstract

The utility model provides a pipe column for a gas injection well, which comprises an oil pipe arranged in a casing pipe, an oil sleeve annulus is formed between the casing pipe and the oil pipe, a check valve is arranged on the oil pipe, and the check valve is arranged in a way that when the pressure in the oil sleeve annulus is larger than the pressure in the oil pipe, the oil sleeve annulus can only be communicated with the interior of the oil pipe. According to the pipe column for the gas injection well, it can be guaranteed that a channel between the oil sleeve annulus and the interior of an oil pipe is closed in the gas injection period, when well killing is needed due to gas channeling, the check valve can be opened in the mode that the oil sleeve annulus is pressed, and therefore a reverse circulation well killing channel is formed, and the well control risk is effectively reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of residual oil exploitation, and in particular relates to a pipe string for a gas injection well. Background Art

[0002] With the continuous deepening of oil reservoir development, the extraction and utilization of residual oil has become an important process for increasing production. Existing oil fields usually adopt gas injection and recovery to extract the residual oil, that is, the residual oil is displaced by injecting nitrogen into a single well. The current unit gas injection string has the following disadvantages: the unit gas injection well has the risk of gas backflow. Once backflow occurs, the conventional gas injection string cannot complete reverse circulation well killing due to the lack of oil-casing connecting device, which poses a great well control risk. Utility Model Content

[0003] One purpose of the utility model is to provide a tubing string for a gas injection well, which can ensure that the passage between the oil-casing annulus and the inside of the oil pipe is closed during gas injection. When well killing is required due to gas channeling, the one-way valve can be opened by pressurizing the oil-casing annulus, thereby forming a reverse circulation well killing passage and effectively reducing the risk of well control.

[0004] According to the present invention, a tubing string for a gas injection well is provided, comprising an oil pipe arranged inside a casing, an oil-casing annulus being formed between the casing and the oil pipe, a one-way valve being provided on the oil pipe, and the one-way valve being configured to allow communication only from the oil-casing annulus to the inside of the oil pipe when the pressure inside the oil-casing annulus is greater than the pressure inside the oil pipe.

[0005] In a preferred embodiment, the inner wall of the oil pipe has a coating, and the coating is used to ensure that the inner wall of the oil pipe is smooth and isolate the oil pipe from the medium inside the oil pipe.

[0006] In a preferred embodiment, the coating is made of graphene material.

[0007] In a preferred embodiment, the gas injection well tubing string further comprises a packer disposed in the oil casing annulus, and the packer is disposed below the check valve.

[0008] In a preferred embodiment, the packer is an HLR anti-corrosion packer.

[0009] In a preferred embodiment, the gas injection well tubing further comprises a slotted screen disposed below the packer, and the slotted screen and the oil pipe located below the packer are both made of stainless steel.

[0010] In a preferred embodiment, the gas injection well tubing string further includes a wire plug provided at the lower end of the oil pipe.

[0011] In a preferred embodiment, the plug is made of stainless steel.

[0012] In a preferred embodiment, the gas injection well pipe string further comprises a tubing hanger provided at the upper end of the tubing.

[0013] In a preferred embodiment, the slotted screen and the oil pipe located below the packer are made of 13Cr stainless steel.

[0014] The utility model has at least the following technical effects:

[0015] According to the utility model, an oil pipe is provided that is disposed within the casing, and an oil-casing annulus is formed between the casing and the oil pipe. A check valve is provided on the oil pipe, and the check valve is configured to allow communication only from the oil-casing annulus to the inside of the oil pipe when the pressure within the oil-casing annulus is greater than the pressure within the oil pipe. This ensures that the passage between the oil-casing annulus and the inside of the oil pipe is closed during gas injection. When well killing is required due to gas channeling, the check valve can be opened by pressurizing the oil-casing annulus, thereby forming a reverse circulation well killing passage and effectively reducing well control risks.

[0016] According to the utility model, the oil pipe below the packer and the slotted screen are made of stainless steel, thereby solving the problem that the coating cannot be formed at the slot position during coating of the slotted oil pipe, and filling the anti-corrosion loophole.

[0017] According to the utility model, the inner wall of the oil pipe is provided with a coating, which is used to ensure the smoothness of the inner wall of the oil pipe and isolate the material of the oil pipe from the medium in the oil pipe, thereby achieving an anti-corrosion and anti-scaling effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The overall structure of a pipe string for a gas injection well according to an embodiment of the present invention is schematically shown.

[0019] In this application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn according to the actual scale. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] In the description of the utility model, it should be understood that the terms "lower" and "inner" etc. indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the utility model.

[0022] In this utility model, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication between two components or the interaction between two components. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to the specific circumstances.

[0023] like Figure 1 As shown, the gas injection well string 100 described in the present invention includes: a tubing 1 disposed within a casing 2, forming an oil-casing annulus between the casing 2 and the tubing 1; a check valve 3 disposed on the tubing 1, configured to allow communication only from the annulus to the inside of the tubing 1 when the pressure in the annulus is greater than the pressure within the tubing 1. It should be noted that the check valve 3 utilizes a large-diameter water and gas injection check valve commonly used in oil and gas well construction. Six single-flow sealing ball valves are designed on the internal piston, and the piston is locked with a shear pin, capable of withstanding high bursting pressures.

[0024] For unit gas injection wells, there is usually a risk of gas backflow due to the low density in the well. Conventional gas injection well tubing cannot complete reverse circulation well killing because it is not equipped with an oil-casing connecting device, which poses a great risk of well control. According to the utility model, an oil pipe 1 is provided inside the casing 2, and an oil-casing annulus is formed between the casing 2 and the oil pipe 1. Since a one-way valve 3 is provided on the oil pipe 1, the one-way valve 3 is configured to: when the pressure in the oil-casing annulus is greater than the pressure inside the oil pipe 1, it can only be connected from the oil-casing annulus to the oil pipe 1, thereby ensuring that the channel between the oil-casing annulus and the oil pipe 1 is closed during gas injection. When well killing is required due to gas channeling, the one-way valve 3 can be opened by pressurizing the oil-casing annulus, thereby forming a reverse circulation well killing channel, effectively reducing well control risks and effectively ensuring the recovery of residual oil.

[0025] In one or more embodiments, the inner wall of the oil pipe 1 has a coating, which is used to ensure the smoothness of the inner wall of the oil pipe 1 and isolate the material of the oil pipe from the medium in the oil pipe, thereby achieving an anti-corrosion and anti-scaling effect.

[0026] In one or more embodiments, the coating is made of graphene material.

[0027] In one or more embodiments, the gas injection well tubing string 100 of the present invention further includes: a packer 4 disposed in the annulus of the oil casing, and the packer 4 is disposed below the check valve 3 .

[0028] In one or more embodiments, the packer 4 is an HLR anti-corrosion packer. Compared to conventional packers, the HLR anti-corrosion packer can achieve corrosion resistance through the spraying of a graphene inner coating and has an improved release mechanism, making it easier to release, avoiding complex overhaul operations and reducing well repair costs.

[0029] In one or more embodiments, the gas injection well tubing string 100 of the present invention further includes a slotted screen 5 disposed below the packer 4. The slotted screen 5 and the oil pipe below the packer 4 are both made of stainless steel, for example, 13Cr stainless steel.

[0030] Conventional slotted screens have the problem of coating failing to form a coating at the slots during coating, creating a weak link in corrosion protection. According to the present invention, the oil pipe below the packer 4 and the slotted screen are made of stainless steel, thus resolving the problem of coating failing to form a coating at the slots during coating of the slotted oil pipe, thus filling the corrosion protection gap.

[0031] In one or more embodiments, the gas injection well tubing string 100 of the present invention further includes a screw plug 6 disposed at the lower end of the oil pipe 1 . The screw plug 6 is made of stainless steel, for example, 13Cr stainless steel.

[0032] In one or more embodiments, the tubing string 100 for a gas injection well according to the present invention further includes a tubing hanger 7 disposed at the upper end of the tubing 1 .

[0033] When injecting gas into the gas injection well string 100 of the present invention, the gas passes through the oil pipe 1, sequentially reaching the check valve 3, the packer 4, the slotted screen 5, the wellbore, and into the formation. The gas then seals the casing annulus via the packer 4, protecting the casing above the packer 4 from oxygen corrosion caused by the injected gas. When gas channeling occurs and the well needs to be killed, wellbore pressure is applied by injecting well fluid into the casing annulus, thereby opening the check valve 3 in one direction and achieving reverse circulation well killing.

[0034] While the present invention has been described with reference to preferred embodiments, various modifications may be made and equivalent components may be substituted without departing from the scope of the present invention. In particular, the various technical features described in the various embodiments may be combined in any manner, provided no structural conflicts exist. The present invention is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A pipe string for a gas injection well, characterized in that: The invention comprises an oil pipe arranged inside the casing, an oil-casing annulus is formed between the casing and the oil pipe, a check valve is arranged on the oil pipe, the check valve is a large-diameter water-injection and air-injection check valve, a plurality of single-flow sealing ball valves are arranged on a piston inside the check valve, and the piston is locked by a shear pin, so that the check valve is set to: when the pressure in the oil-casing annulus is greater than the pressure inside the oil pipe, communication can only be allowed from the oil-casing annulus to the inside of the oil pipe; The gas injection well pipe string further comprises: a packer arranged in the oil casing annulus, the packer being arranged below the check valve, and the packer being an HLR anti-corrosion packer.

2. The pipe string for gas injection well according to claim 1, characterized in that: The inner wall of the oil pipe is provided with a coating, and the coating is used to ensure that the inner wall of the oil pipe is smooth and isolate the oil pipe from the medium inside the oil pipe.

3. The pipe string for gas injection well according to claim 2, characterized in that: The coating is made of graphene material.

4. The pipe string for gas injection well according to claim 1, characterized in that: Also includes: A slotted screen pipe is arranged below the packer, and both the slotted screen pipe and the oil pipe below the packer are made of stainless steel.

5. The pipe string for gas injection well according to claim 1, characterized in that: It also includes a thread plug arranged at the lower end of the oil pipe.

6. The pipe string for gas injection well according to claim 5, characterized in that: The wire plug is made of stainless steel.

7. The pipe string for gas injection well according to claim 1, characterized in that: It also includes an oil pipe hanger arranged on the upper end of the oil pipe.

8. The pipe string for gas injection well according to claim 4, characterized in that: The slotted screen and the oil pipe located below the packer are made of 13Cr stainless steel.

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